1. Field of the Invention
The present invention relates to the preparation and use of benzotriazole compounds. More particularly, it relates to benzotriazole compounds having vinyl groups which can act as monomers for homo- and copolymerization. It also relates to homopolymer or copolymers of benzotriazole compounds having vinyl groups. The most effective application of these materials is in the ultraviolet protection of plastics, wood and other organic materials.
2. Description of the Prior Art
Plastics used in outdoor are exposed to deleterious solar radiation of a wavelength of 290-400 mm(m.mu.). The polymer chain or functional group of the polymer exposed to solar radiation absorbs ultraviolet radiation and is excited to a higher energy level, and there is the possibility that certain photochemical reactions are caused. The photochemical reaction could cause degradation of polymer chains, formation of crosslinkage, or the introduction of functional groups in to the plastic material. An ultraviolet absorber is usually incorporated into plastic material in order to protect it from degradation caused by solar radiation. Ultraviolet absorbers absorb most or all of the harmful radiation. Ultraviolet emit them as harmless radiation and also absorbers photoexited energy in the polymer and emit it as harmless energy, which is necessary for stabilizing polymers. Ultraviolet absorbers should be effective for a long time. It is preferable that the ultraviolet absorber does not cause deterioration or discoloration of the plastic material or should not be leached out in contact with a solvent or the other lower molecular weight material. The peak absorption of the ultraviolet absorber should be in the most sensitive wavelength at which the polymer is used. The optimum effect of ultraviolet absorber for protecting plastic materials from harmful effect of solar radiation should be considered from the point of view of photochemical properties and other functions. For example, it is not enough to have only a high absorbancy index (extinction coefficient) in an ultraviolet region and nondestructive emission of absorbed energy. In general, the most important factor for the selection of ultraviolet absorbers is not only the photochemical property. It is necessary for the ultraviolet absorber to have desired photochemical properties, for example, to have a high absorbancy index in the wavelength region of 300-350 nm. The ultraviolet absorber should be stable and not color or decompose on exposure solar radiation. In order to be not colored the ultraviolet absorber preferably has low absorbancy in the long wavelength region. If the ultraviolet absorber should be considered for preventing sun-burn it should be effective for a long time. The cosmetic ultraviolet absorbers should have low toxicity without any allergic effect. Moreover, the tissue toxicity in penetration into skin should be also low. For example, low molecular compounds such as .beta.-aminobenzoic acid derivatives and salicylic acid derivatives are not satisfactory. The effect of polymeric ultraviolet absorbers depends upon the molecular weight and its volatility. Polymeric ultraviolet absorbers having low volatility and low leachability are preferable. In 2-hydroxy-4-alkoxybenzophenones, this has been attempted but not achieved satisfactorily by having a long alkoxy group, which also improves the compatibility with the polymer. Especially with hydrocarbon polymers compatibility is increased and volatility is decreased by the increase of the length of side chain groups, for example, to the length of the dodecyloxy group.
Polymeric ultraviolet absorbers have been known in prior arts. 2-Hydroxy-4-methacryloxybenzophenone is obtained by reacting 2,4-dihydroxybenzophenone with methacrylic acid derivatives. Other derivatives have been obtained from 2,4-dihydroxybenzophenone. For example, the allyl ether of 2,2',4-trihydroxybenzophenone and 4-chloromethylstyrene. Allyloxy, acrylamino, methacrylamino, vinylsulfoxy and vinyloxy derivatives of 2-(2-hydroxy-5-phenyl)benzotriazole have also been described and their copolymerization with such a comonomer as styrene, acrylonitrile or butadiene are claimed.